There have been known an image forming apparatus having a roller such as a cleaning roller for temporarily holding attached matter such as residual toner attached on a surface of a photosensitive drum. For example, the related-art image forming apparatus is configured to temporarily collect attached matter by the cleaning roller during image forming and reattach the attached matter onto the photosensitive drum after the image forming terminates, so as to collect the attached matter through the photosensitive drum and a conveyance belt.
In this process, a bias is applied to the cleaning roller such that: in a case of collecting the attached matter, the attached matter moves from the photosensitive drums to the cleaning rollers; and in a case of reattaching the attached matter, the attached matter moves from the cleaning rollers to the photosensitive drums.